Investors keen to capitalize on rallying crude-oil prices may increasingly be able to do so by buying and selling commodity-based exchange-traded funds.

INVESTORS KEEN TO CAPITALIZE on rallying crude-oil prices or a weather scare in corn may increasingly be able to do so by buying and selling commodity-based exchange-traded funds. And this, in turn, could affect prices of the commodities underlying the ETFs.

"Most of the flavors of equity-index funds are pretty much covered several times over by ETFs," says Dan Culloton, a mutual-fund analyst at Chicago-based Morningstar....